Russia's hopes for reinstatement before the end of the 2018 PyeongChang Winter Olympics could face a hurdle after another doping charge surfaced.

The Court of Arbitration for Sport said that it has initiated a procedure involving Alexander Krushelnitsky, who tested positive for a banned performance enhancing drug. But no hearing date has been fixed.

Krushelnitsky along with his wife Anastasia Bryzgalova won bronze in the mixed doubles curling in Pyeongchang.

The International Olympic Committee (IOC) said another failed doping test could prevent the Russia delegation from marching under their national flag, during the closing ceremony slated for Feb. 25.

The IOC suspended the Russian Olympic committee last year due to a massive doping scheme at the 2014 Sochi Olympics, but allowed 168 athletes to compete under a neutral uniform and flag known as the Olympic Athletes from Russia (OAR).

Russian curling athletes are puzzled on why anyone would use drugs that aid endurance in a sport that requires steady hands and concentration rather than physical fitness.

"We were all shocked at the news. We very much hope it was some kind of mistake," Russian curler Viktoria Moiseeva told reporters. "With us it's not faster, higher, stronger; it's about being more accurate. I don't know any drugs you could use in curling, so it's very hard to believe."

Russian Curling Federation president Dmitry Svishchev told The Associated Press that Krushenlnitsky was clean as recently as Jan. 22, a day before he departed to the pre-Olympic training camp in Japan.

It was possible someone spiked Krushelnitsky's food or drink with meldonium (a substance that was banned in 2016) said Svishchev. He pointed to the possibility of rival Russian athletes or Russia's political enemies for the spiking.

The curling team brought along a few athletes that weren't qualified for the Olympics as practice partners during pre-Olympic training in Japan.

Before Meldonium was banned, the drug was popular among Russian athletes, as it is known to increase blood flow and improve exercise capacity.

"It can't happen at the Olympic Village because everyone eats the same canteen food," he said. "It could happen at training camp or in the intervening period. There's a possibility of it being something within the team, that something happened during training camp, or as a political means to achieve some goal."

Krushelnitsky's first doping test came out positive and a second sample is being tested with the results due within 24 hours, said the IOC.

If confirmed of doping, the Norwegian team who finished fourth will receive the bronze medal by default.